Mohamed ElBaradei, the Nobel Peace Prize winner, is beginning to emerge as the unifying voice of the opposition in Egypt.

Though lacking deep support on his own, Dr. ElBaradei, a Nobel laureate and diplomat, could serve as a consensus figure for a movement that has struggled to articulate a program for a potential transition. It suggested, too, that the opposition was aware of the uprising’s image abroad, putting forth a candidate who might be more acceptable to the West than beloved in Egypt.

In scenes as tumultuous as any since the uprising began, Dr. ElBaradei defied a government curfew and joined thousands of protesters in Liberation Square, a downtown landmark that has become the epicenter of the uprising and a platform, writ small, for the frustrations, ambitions and resurgent pride of a generation claiming the country’s mantle.

“Today we are proud of Egyptians,” Dr. ElBaradei told throngs who surged toward him in a square festooned with banners calling for Mr. Mubarak’s fall. “We have restored our rights, restored our freedom, and what we have begun cannot be reversed.”

Dr. ElBaradei declared it a “new era,” and as night fell there were few in Egypt who seemed to disagree.

Meanwhile, the Obama administration is doing a delicate tightrope walk between calling for the downfall of a leader of an important ally in the Middle East and being the last Western leader to support a regime that has ruled with an iron fist for almost thirty years. Secretary of State Hillary Clinton called for an “orderly transition,” which a polite way of telling President Mubarak to head for the exit without looting the treasury or killing a lot of people. As it is, the White House is already preparing for dealing with an Egypt without Mr. Mubarak.

One former senior administration advisor said he had spoken to his old colleagues inside the Obama administration in recent days about the unrest in Egypt. As early as last Wednesday, the Obama administration recognized that they would not be able to prop up the Mubarak regime and keep it in power at all costs, the former official said.

“They don’t want to push Mubarak over the cliff, but they understand that the Mubarak era is over and that the only way Mubarak could be saved now is by a ruthless suppression of the population, which would probably set the stage for a much more radical revolution down the road.”

As they say in diplomatic circle, the situation is “fluid.”

One thing that is pretty clear is that here in the U.S., the situation in Egypt is already creating political fallout. The supporters of the Bush administration’s approach to democracy in the Middle East — invade and let the people see what wonderful things Twitter and Taco Bell are — are taking credit for the uprising. Well, I’m no expert on the intricacies of the Middle East, but I kind of doubt that the people of Cairo were all gathered around reading Mr. Bush’s book and decided then and there to take to the streets. And there’s a great deal of difference between a popular uprising in Cairo and a preemptive invasion by the 82nd Airborne. And it’s really risky when we don’t yet know the outcome. What if Egypt becomes the next Iran? Well, I’m sure there’s a way for the Bushies to blame that on President Obama, and take credit if it doesn’t.